Cutter for producing gears



Sept.- 21, 1943.

- E, WILDHABER CUTTER FOR PRODUCING GEARS Filed May 25, 1940 2Sheets-Sheet 1 L ERNEST w/Lomam u e j q ttorneg E. WILDHABER CUTTER FORPRODUCING GEARS Sept. 21, 1943.

Filed May 23, 1940 2 Sheets-Sheet 2 Fit/9: t3 Zhwentor E BN5 5 7' W//.DHHEEE 8g a e Z/ZTTOIIMQ Patented Sept. 21, 1943 *PJ U ITE v Ami-airwa'agwnrsen1t"336 757 1 12,0laih'1s. (01};

"The present invention relates to the-production of gears andparticularly to the produotion of longitudinally curved) tooth gearssuch as spiral bevels an'd hypoid gears; v r It is common practice tolapfthe two meinbers of apair of; spiral or 'hypoid gears together}after theyhave beencut and 'hardened. The lapping operation is performedin order tosrriooth up the" tooth surfaces of the gears and torestorethe tooth hearingor contact which" it is desired to have betweentheir mating tooth surfaces. If no provision is made,vhowever, to reducethe-amount; of" oontact between the mating tooth 'suriaee's during thelapping operation, it is usually found that the (bearing oroontactbetween the ears, after they have beenlapR d, is excessively heavyadjacent the tops of the teeth of the gear or larger member of the pair.This heavy bearing seems to be inreality an interference betweenthe'fteeth and hence is commonly called in the trade ajftop lineinterference? Inany eventit is objection able; for gears which have arenoisy in operation. 7 l It is well known that-topline interference canbe completely avoidedbyvcutting the pinion or smaller niembe'r of a pairoftspiral bevel or hypoid gears with a face-millcuttersuchasdescribed'in the pending application iof; Frederick .EgjMo'Mul';

len, fierialfNo. sai sgffild'oim 2, 1936. outterhas cllttinig edgs ofonejpressilreiangle for cutting the greater portion of the height of thepimp-nteethlandcutti g edgsFof asinaller res sure angle forrelieving'fthe pinion'teeth zithe cledendunn, it'l'lec nge g'esoris'mauer presg surea'ngle cut the in lionteethgbaoknearltheir rootssothat cont t carl not occur more lapping operation betwee; ;.-thepinion'teethf-an ,Tthose no s h mat ng itb thsu a f h s which are.adjagenti the tips of the lge'arj teetht Hence when the pinion teethhavebeen outwith aj 'otter such as idescribedin the Mclvlulle 5pm 1 came,possibility of formation of a topline bear-1 ingiin the ensuing lappingoperation is, eliminated;

While the vMcMullenT cutter and proce'ss h'as;

topline interfer'ence,

thereforesolved the proble'm of opline jmte'rrea once; the present,process presents sorne additional advantages; whenlfreliei is',Iprovided near the: rams of the'pinionteeththe r'elief'isiin' efict; anun ercut; Moreover; When'fthesides, the pin;

ienfteethnarlthev mas er the't'ethare generated to a sfna'ner p rssurej;ang1 ,"than ,the'fgreaterf portion or 'the height am ne teeth thenee s1irfacesnearlthe'ro V ie ba i e known that fatigue failure's'ingears frequently 5'5 n momma Ernest Wildhaber, nrightdni n. Y'as siginorGleason Works, 'Roche'ster,"N. Y.', a corp at the junenable spiral:"b'eveli and 'hypoi'd gear :pairs' to: be

produced, which maybe lapped without introducing toplineinterferencasbut which will have "the advantage that bothgearaandlpin'ionteth have v maximum strength, and smooth; Well-roundedtooth surfaces at the roots oftheijr teeth v a V "A furtheranaindependent object oiithe 'inven tion is' -to-piovide "a face-mill "gearfcutterwvith wh ich tooth s aces of 9, ta red' g'eali" mayfbesimultaneously roughed or finished and the-teeth of the tapered g'earohamferedalon'g their lengths cture ofthe top and side'surfaces of theOther-objects or the"mv'entignlW'illbe apparent hereinafter frorn-thespec'iifloation and from "the recital-of theappended claims; I 5 1 Withthe presentinvention neither gear nor pinion haste'eth relieved near" deeimum' pomjgne-br theteth'of both-members of the pair can;be cut-withcuttingedges off'the same pressure angle as 3 the cutting edges whichform the adderldurn'fp rtionsflofftheflteeth v Smooth,' well roun dedtooth;surtaces at the roots of h t m r e te qr bg vid d on b tInembers'of: the pairiand the teetlr of both me nbers of ;the pair maybe made freeof undercut d erfivr fim imu s th... P s bi t of'formationof topline bearing inthelapping. avoided by chamfering the top edges; ofthe gear.

teeth along their lengths, Whenithe ohamiered gear is run with its matepinion in thella-pping operation; there is'no e ontact 'between thegporation of the tooth surfaces of the gear adjacent .the

ping operation; since the pinionfteeth areicuti with a facermill,cutter1 having cutting 'edges of oneiliressure angleior theirfullheight, the pinion teethwill be stronger than relieved teeth and alsowill be substantiallyfree from scratches near the roots of theteeth.The, chamfering of the gear teeth" at the topswill notafi eotlthestrength of these teeth andhence thepair itseltf produced by the presentinyentionjvill be stronger and have sinoother to'othsurfaces than a pairin hichth'e' teeth 'of the pinion have been relieved. K The inventionhas a further advantage that the chamfering of the corners at thetopofthefgear teeth removes the' sharp corners frorn the teeth vvhieh againis of special'value particularlyin aeroplane iformedat'thejunctures oftheyop'posite side sur- .slots, which. carry stocking .iblades,chamfering -faces21- and 28 withgthe tips,.30:of teeth adjacent ,thetooth space that, is being cut, are chamfered.

- Fig. 3 illustrates diagrammatically thetpaths of bottom and inside andoutside chamfering blades in the cutting of a gear G. Theblades areshown in full lines after they have passed through the "cut." The shadedportion '32 denotes the cut taken in thebottom 3| of a tooth space bythebottom-cutting blade and the shaded portions -;33 .and ,34 denote,respectively, the'cuts taken. on

the opposite corners of teeth 26 by thezopposite .jchamfering blades l5and IBM- When thetooth space has been cut to, full depth the cutter isWithdrawn and the blank is'indexed. .1

The bottom-cutting blades [Zarepreferably sharpened with a hookasdescribed in the Stewart and Candee application :above mentioned"...The .chamfering blades l5 and I6 may.a1sobe'sharpened with hooks. Inthis way the frontface's of the bottom-cutting blades and of thechamfer+ing blades can be aligned with one another and sharpened simultaneously.Hence. the-sharpen: ing operationon thejpresent cutter may: be per.-v

formed as readily .as. the sharpening; or r the ,Stewart and Candeecutter;

It will be noted that the chamfeeng'baoesiis and it have outside andinside cutting edges .40

and "5!, respectively, which areof. greater. pressure angle orinclination totheptaxis H .ofthe cutter than the correspondingside-cutting edges .42 and 33,,respectively, of the side-cuttingbladesl3 and M. It will be noted further that the inside'cutting edges H ofthe inside chamfering blades l6 have a greater pressure angle thanttheoutside cutting edges 40 of the outside chamfer-v ing blades I5. Thetangent of the pressure angle of the cutting edge ofv the insidechamfering blades is ordinarily more than 50% larger than tangent of thepressure angle of the cutting edge of the outside chamfering blades andordinarily the pressure angles of the inside chamfering edges is' morethan twice as large as the pressure angles of the inside side-cuttingedge 42 -of the blades 13. i 7' The radial positions of the chamferingblades and the pressure angles of their side-cutting edges are sorelated to one another and to the root and face angles of the gearwhichis to be'cut that the chamfering edges 4| which cut thecorners ofthe'convex sides of thegear teeth. and the chamiering edges All whichcut the corners. at the concave sides of the gear teeth .may' follow theteeth along their full length, despite .the. taper in depth of theteeth, and chamfer the corners of. the teeth alongtheir fulllength. Thepressure angle to housed on the chamfering blades may becomputed fromthis requirement, ormay be. determined experimentally. Fig. 4 shows atooth ofa gear-produced according to the present invention. .35 and3611c?- blades. which are of the properpressure'angle .and set r to theproper radius; to, chamfer the a way similar tothe cutter illustrated inthe .McMullen et al. patent that is, the. combined cutter may beadjusted to full depth and rotated in engagement with a roughed gear tofinish-cut and chamfer teeth of the gear on each revolutionof .thecutter, the gear being indexed when the gap inthecutter'isabreast of theblank. r

'It will also be understood that while the inven i ion hasv beendescribed specifically in iconnec tionwiththe use of a cutter having afinite num-, 'ber of blades, it is also applicable; where the cut- ;terisvinthe 'form of a grinding wheel-which is in effect a cutter having aninfinite number of cutting edges or blades. The termcutter as used inthe specification and claims is intended, there- .fore, -to includealsoa grinding Wheel; In general it may be said thatwhile the inventionhas been illustrated in connection with a particular embodiment thereof,itwill. be under: stood that the invention is capable of various furthermodifications and this. application is intended to cover any variations,uses, or, adaptae tions of the invention following, in general, theprinciples of the invention and including. such departures fromthepresentdisclosure as come withinknown or customary practice in theartto which the invention pertains and as may be applied to theessential features hereinbefore set ing the top edges of the teeth;thel'atter'blades axis of the cutter from the first blade-sand hav notethe chamfered top corners at-oppositesides of the tooth. i While theinvention has been described iniconthe teeth have been roughed out.Thus, the wellknown single cycle type of gear cutter, such as.illustrated in the U. S. patent, to McMullen, No."

2,125,943 of August 9, 1938 may be employed with modification forpracticingthe present, invention by adding or. substituting in some ofthe blade;

being arranged at a different radial distance from. the axis of thecutterfrom. the first named blades and being arranged to cut in adilferenttootth space fromthe first named blades.

2. A face-mill gear cutter having ..a plurality of blades for cuttingthe side surfaces of the teeth ofa'gear and a plurality of blades forchamfering the top edges of theteeth, theilatter blades being arrangedat different radial distances from the ing opposite side-cuttingedges-whose inclinationwto the axis of the cutter is greater thanxtheinclination of corresponding side-cutting edges of the first'blades andbeingarranged to .cut. in different tooth :spaces from the first namedblades. r

.3. A face-mill gear cutter havinga plurality of blades for chamferingthe topedges of longitudinally curved tooth gears,'said blades havingside-' cutting edges whose inclination to the axis of the cutter isgreater than the pressure angles of the side surfaces of the gear'tobecut, and said blades being arranged at a radial .distance' frcmtheaxis of the cutter which isdifferent from the radius of'lengthwisecurvature of -'the teeth of thegear to be cut.

4. 'A face-mill gear cutter having a plurality of blades-for cutting theopposite side surfacesof" the teeth of a gear and a plurality of bladesfor chamfering the top edges of the teeth, the latter blades beingarranged to cut in a difiere'nt tooth space of the gear from thefirst-named blades, certain of the. chamfering blades having sidecuttingedges for I chamfering the top corners one-side -of -the te'ethi of thegear and'being at rangedat a greater radial distance from the axis ofthe cutter than the first named blades, and

others :of the chamfering blades having sidemttance from-the axis-of thecutter than the first named blades, and others of the cham fering bladeshaving inside cutting edges and being arranged at a lesser radialdistance'froin the axis ofthe cutter than the firstnamed bladestlae saidoutside and inside cutting edegs of the chamfering blades -being" *bo'thinclined at-a greater angle to the axis of-the cutter than thecorresponding side-cutting edges of the-first named blades, and theoutside chamfer'ingedges being less inclined to the axis of the cutterthan the-inside chamferingedges. a k I,

6. A face-mill gear cutter having-a plurality of side-cutting blades, aplurality of bottom-cutting blades, and a plurality of chamferi-ngblades, "the bottom-cutting blades alternating with 'the sidecuttingbladesaround the periphery bf the *head and projecting axially beyondthe side-cutting blades and having opposite side edges ofs mallerpressure angle than corresponding edges of the side-cutting blades, thechamfering blades being radially aligned with the bottom-cuttingblades', certain of the cha-mfering' blades having outside cuttingedges, and others of the chamfer'ing blades having inside cutting edges,the chanifer ing blades with outside cutting edges :being positionedradially at a greater distance from the axis of the cutter than thebottom-cutting blades, and the chainfering blades with inside cuttingedges being positioned'radially of the axis of'the cutter at a lessdistance than the .bottoimcutting blades, the outside and inside cuttingedges of the chamfering blades being inclined tolthe aids of the cutterat a greater angle than the. corresponding side-cutting edges of theside-cutting blades, and the inclination of the inside cutting edges ofthe chamfering blades being greater than the inclination of the outsidecutting edges-of the chamfering blades. I T i '7. A face-mill gearcutter having a plurality of blades for chamfering thetop edges oflongitudinally curved tooth gears, certain of the blades having outsidecutting; edges for chamfering one side of the teeth of the gear at thetop thereof, and other blades having inside cutting edges'io'r.chamfering the opposite side of the teeth of'the gear at the topthereof, both said outside and said inside cutting edges being ofgreater inclination of the axis of the cutter than therpre'ssure angleof the sides of the teeth to be chamfered'and the outside chamferingblades .beingm'ounted in the cutter at a sufficiently greater'radialdistance from the axis of the cutter than the inside ihamfering bladesto operate on oneside or" a tooth space that isspaced from thetooth's'pacecn whose side the inside-blades operatei e eastoa 8. niiacemh gear cuttewhavihga pluralitycf iblades for'chamfring bhe Ztopedg'esof longitudimug curved-tooth gears, certainof'said blades ioutsidecuttingedge's for chamfering one side or i the-teeth: of a gear at thetops thereof, and other Ibladeshaving' insideicutting edges forchamtering theopposite sides of the 'teeth at the tops thereoi,Lbothsaid inside and said outside cutting -edgesflbeing inclinedto theaxis cit-the was atlian angle greater than the: pressure anglesot theside' tooth surfaces of'the gearto b ohamfered and the outside'andinside cham fering blades beingmeunted radially at different distancesfrom-the ax is of the cutter head so that the outsidelblade's o ierateonone side of a tooth 'siaa'ce "thatis spaced zf-rom the tooth space onwhose side the inside blades operate. I

9'. A' f-aee' mill gear'ficutter having a plurality of' blades forchamfering the top edges of longi- 'tudinally: curved toothgea-rs',icertainof the blades having: outsidecutting edges forchamiering one side of the teeth xio fl'a-"g'eaiiat the tops thereof,and other blades having J inside cutting edges for ehamferingtheopposite sides of the teeth at the tops thereof, 'thei insid'eo'hanrfering edges being inclined at a greater a'ngle tothelakis of thecutteri-than'theoutsideeham'deririg edges, and both the-inside andoutsidechamf-ering edges being inclined to the axis of'the cutter atanglesg-reater than the pr'essur angles of the side tooth surfaces ofthe-gear l'to b'e cham'fered, the outside andinside-chamferingubladesbeing mounted radially Lat different distancesfrom :the axis of the cutter head so that the outside blades operateonmne's'idejlofa to'othspaoe that is spaced from the itooth space onwhose sidethe inside blades operate 1. i

' iluia'face mill gear: cutter having a plurality ofblades' ior cuttingthe opposite side surfaces of the teeth o'f a lgear and a-plura'lity ofblades for chamfering' the to'pedgesof the teeth, the latter bladesbeingarranged to cut indifferent tooth spaces of the 1 gear from the first:na-med blades, certain of the 'charnfering blades having side cuttingedges for chamfering the top corners at one side of theteeth ofagearandbeing arranged at a 'greater "radial' distancefrom theaXis ofthe cutter'thain the first na'med blades, and others oftheLchamfieringlblades having-side cutting edges for chamferingthe':to'p corners at the opposite side oi' the teeth ofithe gea-r andbeing arranged at a lesser radial distance from the axis of the cutterthtm'lth'e first named lblades. 11. A'iao mill gear cutter having-'24plurality of blades"for cutting the' opposi'te sides of the teeth "ofagear-and a' plurality of blades for chamtei ing the top "ledges 0f "theteeth, certain of tli'e'- chanifering"blades-"having side cutting edgesfor chamfering the top corners at one side of the teeth-lofthe gear and-being arra nged at ao'greater radial-distance tram the axis-of thecutter than: the first named blades other of the chamfering bladeshaving side cu ttiiigetlges for eharnfering thewtop corne-rs at theopposite side 'of the teeth of the gear and being arranged at a l'e'ssereasier distance em the; axis of the cutter than th first 'named blad'es,whereby the tu o' group's of chamfering blades may operate in men snaceslying' at opposite sides", respectively,

of-the tooth space 'in w'hich the first named blades opera/to",- botli-grouns of chamfering blades'having their-side edges inclined Ito-the"axis of the cutter at 'a" greater' anglec than the cor-responding sideedgesdf the first named blades, andthe chamteriing blafde's which arear-ranged -at the greet'er chamfering one side of the teeth at the tops1 thereof, andothers of said blades having inside cutting edges forchamfering the other sides of said teeth at the tops thereof, both saidinside and said outside chamfering edges being inclined to the axis ofthe cutter at angles greater than 15 the pressure angles of the sidetooth surfaces to be chamfered, said outside chamfering edges beinginclined to the axis of the cutter at an angle less than the insidechamfering edges, and said outside chamfering edges being arranged at agreater radial distance from the axis of the cutter than said insidechamfering edges and being spaced from said inside chamfering edges asufficient radial distance to operate on the concave side of a toothspace of the gear to be chamfered that is spaced from the tooth space onthe convex side of which the inside chamfering blades operate.

ERNEST WILDHABER.

